diff --git a/lib/DOM/Document.php b/lib/DOM/Document.php
index 18c000f..40fcc04 100644
--- a/lib/DOM/Document.php
+++ b/lib/DOM/Document.php
@@ -50,15 +50,19 @@ class Document extends \DOMDocument {
 
     public function createAttributeNS($namespaceURI, $qualifiedName) {
         try {
-            return parent::createAttributeNS($namespaceURI, $qualifiedName);
+            $out = @parent::createAttributeNS($namespaceURI, $qualifiedName);
         } catch (\DOMException $e) {
             // The element name is invalid for XML
             // Replace any offending characters with "UHHHHHH" where H are the
             //   uppercase hexadecimal digits of the character's code point
             $this->mangledAttributes = true;
             $qualifiedName = $this->coerceName($qualifiedName);
-            return parent::createAttributeNS($namespaceURI, $qualifiedName);
+            $out = parent::createAttributeNS($namespaceURI, $qualifiedName);
         }
+        if ($out === false) {
+            throw new \DOMException("Document element must be inserted first");
+        }
+        return $out;
     }
 
     public function createElement($name, $value = "") {
diff --git a/lib/DOM/Element.php b/lib/DOM/Element.php
index 160e551..679982d 100644
--- a/lib/DOM/Element.php
+++ b/lib/DOM/Element.php
@@ -50,52 +50,54 @@ class Element extends \DOMElement {
     }
 
     public function setAttribute($name, $value) {
-        try {
-            // If setting a class attribute and classList has been invoked use classList to
-            // set it.
-            if ($this->_classList !== null && $name === 'class') {
-                $this->_classList->value = $value;
-            } else {
+        // If setting a class attribute and classList has been invoked use classList to
+        // set it.
+        if ($name === 'class' && $this->_classList !== null) {
+            $this->_classList->value = $value;
+        } else {
+            try {
+                parent::setAttribute($name, $value);
+            } catch (\DOMException $e) {
+                // The attribute name is invalid for XML
+                // Replace any offending characters with "UHHHHHH" where H are the
+                //   uppercase hexadecimal digits of the character's code point
+                $this->ownerDocument->mangledAttributes = true;
+                $name = $this->coerceName($name);
                 parent::setAttribute($name, $value);
             }
-        } catch (\DOMException $e) {
-            // The attribute name is invalid for XML
-            // Replace any offending characters with "UHHHHHH" where H are the
-            //   uppercase hexadecimal digits of the character's code point
-            $this->ownerDocument->mangledAttributes = true;
-            $name = $this->coerceName($name);
-            parent::setAttribute($name, $value);
-        }
-        if ($name === "id") {
-            $this->setIdAttribute($name, true);
+            if ($name === "id") {
+                $this->setIdAttribute($name, true);
+            }
         }
     }
 
     public function setAttributeNS($namespaceURI, $qualifiedName, $value) {
-        try {
-            // If setting a class attribute and classList has been invoked use classList to
-            // set it.
-            if ($this->_classList !== null && $namespaceURI === null && $qualifiedName === 'class') {
-                $this->_classList->value = $value;
-            } else {
-                parent::setAttributeNS($namespaceURI, $qualifiedName, $value);
+        // If setting a class attribute and classList has been invoked use classList to
+        // set it.
+        if ($qualifiedName === 'class' && $namespaceURI === null && $this->_classList !== null) {
+            $this->_classList->value = $value;
+        } else {
+            try {
+                // NOTE: We create attribute nodes so that xmlns attributes don't get lost
+                $a = $this->ownerDocument->createAttributeNS($namespaceURI, $qualifiedName);
+            } catch (\DOMException $e) {
+                // The attribute name is invalid for XML
+                // Replace any offending characters with "UHHHHHH" where H are the
+                //   uppercase hexadecimal digits of the character's code point
+                $this->ownerDocument->mangledAttributes = true;
+                $qualifiedName = $this->coerceName($qualifiedName);
+                $a = $this->ownerDocument->createAttributeNS($namespaceURI, $qualifiedName);
+            }
+            $a->value = $this->escapeString($value, true);
+            $this->appendChild($a);
+            if ($qualifiedName === "id" && $namespaceURI === null) {
+                $this->setIdAttribute($qualifiedName, true);
             }
-        } catch (\DOMException $e) {
-            // The attribute name is invalid for XML
-            // Replace any offending characters with "UHHHHHH" where H are the
-            //   uppercase hexadecimal digits of the character's code point
-            $this->ownerDocument->mangledAttributes = true;
-            $qualifiedName = $this->coerceName($qualifiedName);
-            parent::setAttributeNS($namespaceURI, $qualifiedName, $value);
-        }
-        if ($qualifiedName === "id" && $namespaceURI === null) {
-            $this->setIdAttribute($qualifiedName, true);
         }
     }
 
     public function setAttributeNode(\DOMAttr $attribute) {
         parent::setAttributeNode($attribute);
-
         if ($attribute->name === 'id') {
             $this->setIdAttribute($attribute->name, true);
         }
@@ -103,8 +105,7 @@ class Element extends \DOMElement {
 
     public function setAttributeNodeNS(\DOMAttr $attribute) {
         parent::setAttributeNodeNS($attribute);
-
-        if ($attribute->name === 'id') {
+        if ($attribute->name === 'id' && $attribute->namespaceURI === null) {
             $this->setIdAttribute($attribute->name, true);
         }
     }
diff --git a/lib/TreeBuilder.php b/lib/TreeBuilder.php
index ace1ae4..7060d79 100644
--- a/lib/TreeBuilder.php
+++ b/lib/TreeBuilder.php
@@ -4150,6 +4150,12 @@ class TreeBuilder {
         # Let element be the result of creating an element given document,
         #   localName, given namespace, null, and is.
         $element = $this->DOM->createElementNS($namespace, $token->name);
+        // DEVIATION: If there is no document (root) element yet, temporarily
+        //   insert this element so that creating attributes for it does not
+        //   fail due to a PHP DOM limitation
+        if (!$this->DOM->documentElement) {
+            $this->DOM->appendChild($element);
+        }
         # Append each attribute in the given token to element.
         foreach ($token->attributes as $attr) {
             # If element has an xmlns attribute in the XMLNS namespace whose value
@@ -4168,6 +4174,10 @@ class TreeBuilder {
                 $element->setAttributeNS($attr->namespace, $attr->name, $attr->value);
             }
         }
+        if ($this->DOM->documentElement && $this->DOM->documentElement->isSameNode($element)) {
+            // Pop off the document element if it was inserted above
+            $this->DOM->removeChild($element);
+        }
         # Return element.
         return $element;
     }
diff --git a/tests/cases/TestSerializer.php b/tests/cases/TestSerializer.php
index d210b1a..73fdfde 100644
--- a/tests/cases/TestSerializer.php
+++ b/tests/cases/TestSerializer.php
@@ -17,7 +17,7 @@ use MensBeam\HTML\Parser;
  * @covers \MensBeam\HTML\Comment
  * @covers \MensBeam\HTML\Text
  */
-class TestTreeConstructor extends \PHPUnit\Framework\TestCase {
+class TestSerializer extends \PHPUnit\Framework\TestCase {
     use \MensBeam\HTML\EscapeString;
 
     protected $out;
@@ -85,6 +85,7 @@ class TestTreeConstructor extends \PHPUnit\Framework\TestCase {
 
     protected function buildTree(array $data, bool $fragment): \DOMNode {
         $document = new Document;
+        $document->appendChild($document->createElement("html"));
         $out = $fragment ? $document->createDocumentFragment() : $document;
         $cur = $out;
         $pad = 2;
diff --git a/tests/cases/tree-construction/mensbeam01.dat b/tests/cases/tree-construction/mensbeam01.dat
index f960495..08a8f66 100644
--- a/tests/cases/tree-construction/mensbeam01.dat
+++ b/tests/cases/tree-construction/mensbeam01.dat
@@ -7,6 +7,7 @@
 |   <head>
 |   <body>
 |     <svg svg>
+|       xmlns xmlns="http://www.w3.org/2000/svg"
 
 #data
 <!DOCTYPE html><svg xmlns="http://www.w3.org/1999/xlink"/>
@@ -28,6 +29,7 @@
 |   <head>
 |   <body>
 |     <svg svg>
+|       xmlns xlink="http://www.w3.org/1999/xlink"
 
 #data
 <!DOCTYPE html><svg xlink:href="http://example.com/"/>